Wash the potatoes and boil them covered with water. Cover and cook for 20 minutes. Drain potatoes, rinse and peel. Cut potatoes lengthwise into quarters. Mix remoulade and yoghurt.
Wash the chives, dab dry and cut into small rolls and stir into the tartar sauce except for a little garnish. Season with salt and pepper. Cut the gherkins into slices. Mix potato quarters and cucumber slices.
Peel and finely chop the onion. Drain tuna well. Knead tuna, onion, egg and breadcrumbs. Season with salt and pepper. Form 8 meatballs from the fish mixture. Heat oil in a pan and fry the meatballs in it until golden brown.
Season salad again. Arrange tuna fish cakes and potatoes with a blob of tartar sauce on plates. Sprinkle with chives and garnish with dill. Remaining tartar sauce extra is enough.